Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor, Slovenia.
Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia.
Molecules. 2020 Jun 26;25(12):2947. doi: 10.3390/molecules25122947.
In this study the effect of growth medium strength on the minimum inhibitory concentration (MIC) of different tannins and tannin extracts against was systematically investigated for the first time. Three pure compounds (vescalagin, castalagin and gallic acid) and five extracts (chestnut, quebracho, mimosa, Colistizer and tannic acid) were studied. Broth microdilution was assayed and bacteria were grown using different growth medium strengths varying from half to double the concentration recommended by the producer. MICs were determined using the iodonitrotetrazolium chloride (INT) dye or turbidity measurements. It was observed that MIC values depend on the growth medium strength. With an increase in the growth medium concentration MIC values rose roughly linearly for all samples, while their relative order remained unchanged, indicating that a direct interaction of tannins with growth medium nutrients represents the likely source of their antimicrobial activity. Understanding the effect of growth medium strength can finally yield a plausible explanation for the observed variation in MIC values reported in the scientific literature as well as provide help in planning proper applications of tannins in the livestock production.
本研究首次系统地研究了生长培养基强度对不同单宁和单宁提取物对最小抑菌浓度（MIC）的影响。研究了三种纯化合物（栗木鞣花单宁、苛性李单宁和没食子酸）和五种提取物（栗木、奎拉乔、含羞草、Colistizer 和鞣酸）。采用微量肉汤稀释法，使用推荐浓度的半倍至两倍生长培养基浓度来培养细菌。使用碘硝基四唑氯化物（INT）染料或浊度测量法测定 MIC。结果表明，MIC 值取决于生长培养基强度。随着生长培养基浓度的增加，所有样品的 MIC 值大致呈线性上升，而其相对顺序保持不变，这表明单宁与生长培养基营养物质的直接相互作用是其抗菌活性的可能来源。了解生长培养基强度的影响，可以最终为科学文献中报道的 MIC 值变化提供合理的解释，并有助于在畜牧业生产中合理应用单宁。
